We propose to prepare a series of new polymers which contain covalently grafted protease inhibitors. We will investigate the blood compatibility of the new polymers and evaluate their usefulness as synthetic materials for blood contact applications. Specifically, known active site-directed inhibitors of thrombin which also inhibit blood clotting and platelet aggregation were grafted to copolymers of methacrylic acid esters and other vinyl monomers to provide new polymers. Initial examination of these new polymers is encouraging as they show strong inhibition of thrombin in vitro. Promising new materials will be coated on catheters and evaluated for thrombogenicity in dogs.